JPH06201377A - Range finder - Google Patents

Abstract

PURPOSE:To calculate distance measurement information from the information obtained by an integrating (A/D converting) means when an amplified signal is lower (higher) than a determined level, and shorten the distance measurement information calculating time of a short-range subject having a high reflectance. CONSTITUTION:Signals SPL1,2 are ON by distance measurement start to form the state capable of emitting light 28 and inputting output signals (A+B) of a light receiving element 1 to an amplifier 12. A timer is reset after the lapse of X ms to extinguish the light 28, and counting is newly started. When the count value reaches X ms, the A-side signal of the element 1 is inputted to the amplifier 12, and when the flag L is O, or the light receipt signal is small (weak), the signal A is top-down integrated for a time T, and subject distance information is obtained from the time t/T bottom-up integrated until reaching the initial value in the signals (A+B). When the count value does not reach X ms, the flag L is set to 1 which shows that the receipt signal is large (strong), the amplifier 12 output is A/D converted by X/2 ms to obtain a value A'D1. When the flag judgement is 1, the value similarly converted 101 is AD2, and when it reaches X ms, the values AD2, AD1 are operated by a determined expression to provide the subject distance information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light projecting means such as IRED for projecting signal light onto an object to be measured, and a PSD for receiving light reflected by the object to be measured by the light projecting means. The present invention relates to an improvement of an active distance measuring device including a light receiving unit.

[0002]

2. Description of the Related Art As is already known, an active autofocus distance measuring method receives reflected light of a projected signal light by a light receiving element such as PSD and reflects the reflected light on a light receiving surface by two signal outputs. The object distance is obtained by detecting the position of the light.

Here, in the prior art, assuming a long-distance, low-reflectance subject, in order to improve the S / N, the light receiving signal is always integrated for a certain period of time, and the subject distance is obtained from the accumulated signal. Was there.

[0004]

However, in the above-mentioned conventional example, the received light signal is always accumulated even if the object is a short distance and has a high reflectance, that is, the received light signal is large (strong). It took a long time to measure the distance because of the time.

(Object of the Invention) An object of the present invention is to greatly reduce the distance measurement information calculation time when the distance to the object to be measured is short or the reflectance is high. It is to provide a distance measuring device.

[0006]

According to the present invention, there is provided an integrating means for integrating an amplified signal from a light receiving means, an A / D converting means for A / D converting the amplified signal from the light receiving means, and the light receiving means. Level determination means for determining whether or not the amplified signal exceeds a predetermined level, and based on the information obtained by the integration means when the level determination means determines that the level is below the predetermined level. The distance measuring information is calculated, and when it is determined that the level exceeds a predetermined level, the distance measuring information is calculated based on the information obtained by the A / D converting means. When it is determined that the amplified signal from the means exceeds the predetermined level, the amplified signal from the light receiving means is immediately A / D converted by the A / D converting means without performing integration by the integrating means. Converted to this A / D conversion information Zui it is possible to calculate the distance measurement information.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the illustrated embodiments.

FIG. 1 is a circuit diagram showing the structure of a distance measuring device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a PSD (semiconductor position detector) which is a light receiving element. Reference numerals 2 and 4 are resistors and reference numerals 3 and 5 are operational amplifiers, which constitute a current-voltage conversion circuit for converting the output current of the PSD 1 into a voltage. 6 and 7 are capacitors for cutting the DC component received by the PSD 1,
8 and 9 are resistors for determining the gain of the next-stage operational amplifier and PSD output voltage addition, and 10 and 11 are one output (A) of the PSD 1.
And a sample analog switch for selecting the other output (B), 12 is an amplifier for amplifying the voltage input via the analog switches 10 and 11, and 13 is a resistor for determining the amplification factor of the amplifier 12. is there.

Reference numerals 14 and 15 are resistors for multiplying the output signal of the amplification amplifier 12 by "-1". Reference numerals 16 and 17 are amplification amplifiers 12.
To convert the output voltage of the amplifier into a current, 18 and 19 are analog switches for selecting the output of the amplifier 12 and the output of an operational amplifier 29 described later, 20 is an integrating amplifier, 21 is an integrating capacitor, and 22 is accumulated in the integrating capacitor 21. It is an analog switch for discharging the electric charge. Reference numeral 23 is a discharging resistor, and 24 is a comparator that determines the output voltage of the integrating amplifier 20, and outputs a determination signal CP2. Two
Reference numerals 5 and 26 have resistance values of R2 and R1 and divide a predetermined reference voltage Vc, and 27 is a voltage obtained by dividing the output voltage of the amplification amplifier 12 and the predetermined reference voltage Vc {Vc · R.
Is a comparator that determines 1 / (R1 + R2)},
The determination signal CP1 is output. Reference numeral 28 denotes an IRED (infrared light emitting diode) which is a light projecting element. Reference numeral 29 is an operational amplifier for multiplying the output voltage of the amplification amplifier 12 by "-1".

Reference numeral 101 designates the output voltage of the amplification amplifier 12 as A /
A / D conversion circuit for D conversion, 102 a drive circuit for driving the IRED 28, 103 a control circuit for the drive circuit 102, and the analog switches 10, 11, 18, 19,
Signals SPL1, SPL for controlling ON / OFF of 22
It is a CPU that outputs 2, SPL3, SPL4, SPL5.

Next, the operation will be described with reference to the flowchart of FIG. 2 with reference to FIGS. 1, 3 and 4.

First, in the initial state, the CPU 103 turns off the signals SPL1, SPL2, SPL3 and SPL4.
Then, the signal SPL5 is turned on, and the charge of the integration capacitor 21 is reset. Further, the flag L indicating whether or not the received light signal is large (strong) is set to "0" (step 101).

Next, simultaneously with the start of distance measurement, the signals SPL1 and SPL
PL2 is turned on, the IRED 28 is made to emit light, and the IRE
The output signal of PSD1 that received the reflected light of D28 is converted into a current-voltage signal, and the sum of the DC-cut signals is set to a state where (A + B) is input to the amplification amplifier 12 (step 10).
2 → 103 → 104). Next, the built-in timer 1 is started and a certain fixed time (“x” ms) is counted (step 105 → 106). Then, after a lapse of a fixed time, the timer 1 is reset, the IRED 28 is turned off, the timer 1 is newly started, and counting is started (steps 107 → 108 → 109).

Next, the count value of the timer 1 is "x".
It is determined whether ms has been reached (step 110).
As a result, if "x" ms has not been reached, step 1
The operations from 11 to 115 are executed.

That is, since the flag L is set to "0" by the time the count value of the timer 1 reaches "x" ms, the comparator 27 which determines the output voltage of the amplification amplifier 12 is determined. The judgment signal CP1 which is the output is checked, and when the judgment signal CP1 is "1", that is, when the output voltage amplitude of the amplification amplifier 12 is large, the flag L is set to "1" (the light reception signal is large (strong)). When the count value of the timer 1 is “x / 2” ms,
The output voltage (A + B) of the amplification amplifier 12 is A / D converted by the A / D conversion circuit 101, and the value obtained at this time is A
D1 (steps 111 → 112 → 113 → 114)
→ 115).

After that, when it is determined that the count value of the timer 1 has reached "x" ms, the timer 1 is reset, then the signal SPL2 is turned off, and only one of the light receiving signals (A side) of the PSD1 is received. Is input to the amplification amplifier 12 (step 110 → 1116 → 117).

Next, it is determined whether or not the flag L is "0", and if "L = 0", that is, if the light receiving signal of PSD1 can be determined to be small (weak), one signal (A) of PSD1. Is down-integrated for a fixed time T, and then PSD1
Both of the signals (A + B) are used to perform the ascending integration until the initial value is reached, and the subject distance information is obtained based on the ratio between the time t required for the ascending integration and the previous constant time T (step 1
18 → P119 → 120 → 121). Since the operation at this time is already known, that is, the operation is the same as the conventional one, further description will be omitted.

FIG. 3 shows the operating state of each part at this time.
Is.

On the other hand, as a result of the determination of the flag L, "L = 1"
In the case of, that is, when it can be determined that the light receiving signal of the PSD 1 is large (strong), the IRED 28 is turned on again, the timer 1 is started, and the elapse of a certain time is waited (step 118 → 122 → 123 → 124). Then, after a lapse of a certain time, the timer 1 is reset, the IRED 28 is turned off, the timer 1 is newly started, and counting is started (step 125 → 126 → 127). And
When the count value of the timer 1 is "x / 2" ms, the output voltage of the amplification amplifier 12 is A / D converted by the A / D conversion circuit 101, and the value obtained at this time is AD2 (step 128 → 129 → 130).

After that, when it is determined that the count value of the timer 1 has reached "x" ms, the timer 1 is reset (step 128 → 131).

Then, in step 132, the A / D conversion value AD2 obtained in the above step 130 and the A / D conversion value AD1 obtained in the above step 115.
Is calculated as shown below.

(Vc-AD2) / (Vc-AD1) (1) As a result of the above equation (1), subject distance information can be obtained.

FIG. 4 shows the operating state of each part at this time.
Is.

According to this embodiment, the means for determining whether the received light signal is a relatively large (strong) signal, and if the received light signal is large to some extent, the amplified signal is directly A / D-converted.
A means for converting and calculating distance measurement information based on the A / D converted value is provided.

As a result, in the related art, since the signal was stored regardless of the distance to the object to be measured (for example, the subject) and the reflectance thereof, the storage time was always required, but according to the present embodiment. , When the received light signal is large (S / N
Is good), that is, the distance to the target object is close,
Alternatively, when the reflectance is high, it is possible to directly A / D-convert the amplified signal without accumulating the signal, and obtain distance measurement information based on this result, which can dramatically reduce the distance measurement time. Become.

(Modification) In this embodiment, the A / D conversion values AD1 and AD2 are values obtained by one A / D conversion operation, but this A / D conversion operation is repeated a plurality of times. , And the average value thereof may be set as AD1 and AD2. FIG. 5 shows the operation state of each part when such an operation is performed.
Is.

Further, the peak of the output voltage of the amplification amplifier 12 may be detected and A / D converted at that time to obtain AD1 and AD2.

The level of the amplified signal of the received light signal is not determined by the sum signal (A + B), but by one of A and B.
It is also possible to perform the A / D conversion by making a determination using only the signal. Further, the sum signal (A + B) exceeds a predetermined level, and the output signal A
Is above a predetermined level, or the summation signal (A
+ B) exceeds a predetermined level and the output signal B exceeds a predetermined level, A / D conversion may be performed.

[0029]

As described above, according to the present invention,
An integrating means for integrating the amplified signal from the light receiving means, an A / D converting means for A / D converting the amplified signal from the light receiving means,
If the amplified signal from the light receiving means determines whether it exceeds a predetermined level or not, and if the level determination means determines that the amplified signal is below the predetermined level,
Distance measurement information is calculated based on the information obtained by the integration means, and if it is determined that the predetermined level is exceeded, distance measurement is performed based on the information obtained by the A / D conversion means. If it is determined that the amplified signal from the light receiving means exceeds a predetermined level, the amplified signal from the light receiving means is immediately obtained without performing integration by the integrating means. To A / D by A / D conversion means
After the conversion, the distance measurement information is calculated based on this A / D conversion information.

Therefore, it is possible to significantly reduce the distance measurement information calculation time when the distance to the object to be measured is short or the reflectance is high.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a distance measuring device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the distance measuring device of FIG.

FIG. 3 is a timing chart showing an operation state of each unit when the light receiving signal is small (weak) in the distance measuring device of FIG.

FIG. 4 is a timing chart showing an operation state of each part when the light receiving signal is large (strong) in the distance measuring device of FIG.

5 is a timing chart showing an operation state of each part when the operation of FIG. 4 is repeated a plurality of times.

[Explanation of symbols]

 1 PSD 12 Amplification Amplifier 20 Integrating Amplifier 21 Integrating Capacitor 25, 26 Resistance 27 Comparator 28 IRED 101 A / D Converter Circuit 102 IRED Driving Circuit 103 CPU

Claims (1)

[Claims] 1. A light projecting means for projecting signal light onto an object for distance measurement, a light receiving means for receiving light reflected by the object for distance measurement from the light emitting means, and an amplified signal from the light receiving means. Integrating means for integrating, A / D converting means for A / D converting the amplified signal from the light receiving means, level determining means for determining whether or not the amplified signal from the light receiving means exceeds a predetermined level, When the level determination means determines that the level is equal to or lower than the predetermined level, the distance measurement information is calculated based on the information obtained by the integration means, and it is determined that the level exceeds the predetermined level. In this case, a distance measuring device comprising a calculating means for calculating distance measuring information based on the information obtained by the A / D converting means.